Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$205.71	3.407%	$212.7185	$212.72	$212.70	$212.70
Purchase #2	$163.80	13.578%	$186.0408	$186.04	$186.05	$186.00
Purchase #3	$57.82	8.791%	$62.903	$62.90	$62.90	$62.90
Purchase #4	$33.90	11.806%	$37.9022	$37.90	$37.90	$37.90
Purchase #5	$178.28	12.411%	$200.4063	$200.41	$200.40	$200.40
Purchase #6	$80.39	10.755%	$89.0359	$89.04	$89.05	$89.00
Purchase #7	$165.69	12.843%	$186.9696	$186.97	$186.95	$187.00
7 purchase totals =	$885.59		$975.9763	$975.98	$975.95	$975.90